Insulator.



A. O. AUSTIN. INSULATORI APPLICATION FILED MAY I2. IBIG.

1 ,242,907. Patented Oct. 16, 1917.

2 SHEETS-SHEET I.

, I 0 iflv ezzior 27574 6; as) r A. 0. AUSTIN.

INSULATOR.

APPLICATION FILED MAY 12, 1916.

1,242,907. I Patented Oct. 16,1917.

2 SHEETS-SHEET 2.

7 Y I M Q v I Z UNITED STATES PATENT OFFICE.

ARTHUR O. AUSTIN, OF BARBERTON, OHIO, ASSIGNOR TO THE OHIO BRASS COMPANY,

OF MANSFIELD, OHIO, A CORPORATION OF NEW JERSEY.

INSULATOR.

Specification of Letters Patent.

Patented Oct. 16, 1917.

Application filed May 12, 1916. Serial No. 96,991.

- glass or some similar material of which the coefficient of expansion is difierent than that of the metal supporting cap. The principal object of the invention is to provide a new and improved construction, combination and arrangement of parts by which any stresses or strains due to the unequal expansion or contraction of the parts, or the bursting or blowing out of the insulator proper, may be permitted without causing the actual separation of the parts or causing the insulator unit to fail mechanically.

In the accompanying drawings, Figure 1 is a view partly in elevation and partly in section, of an insulator having a thin portion around the upper part of the cap; Fig.

2 shows an insulator with a cap having openings for relieving internal pressure; Fig. 3 shows an insulator with a cap having weakened portions at intervals around the top; Fig. 4 is a sectional view taken on the line 44 of Fig. 3; Fig. 5 shows an insulator cap with partiallv cut out weakened portions; Fig. 6 shows a portion of a perforated insulator cap with a yielding material filling the opening; and Fig. 7 is a view taken on the line 77 of Fig. 6 showing the parts and opening in section.

It has been found in insulator practice, that an insulator unit may occasionally burst or explode, due to abnormal pressure caused by the unequal expansion or contraction of the insulator parts, or by the failure of the insulator unit electrically due to a high voltage. If the insulator unit does not come apart and permit the line suspended by it to drop, it'is possible that an inslulator composed of several insulating units may still have some good members which will permit the line to beenergized and operated normally without the removal of the-defective member. If, however, the insulator fails mechanically, so that the parts separate and the line is dropped, re-

pairs must be made before the line can be again placed in operation. I

If the insulator unit is subjected to a severe electrical strain, such as a flash-over, or a high potential discharge, it may happen that the insulating member of a 'unit becomes'punctured and an arc is established between its connecting pin and metal suspending cap. Theare established may volatilize material with which it comes in contact, setting up a very high pressure which tends to force the porcelain or pin out of the cap, permitting the line suspended by the insulator to drop.

' The present invention relates toan insulator suspended by a metal cap which is so constructed that it will relieve an abnormal pressure within the metal cap due to the threatened bursting or the electrical failure of the insulator, without causing the mechanical failure of the insulator unit.

As shown in Fig. 1, an insulator proper, composed of porcelain, glass or any suitable material, is formed with a projecting flange 4 and a central head or boss 5 which is inserted within a cup-shaped recess 6 of an insulator cap 7. This cap is formed with a straight lower edge,-as shown in Fig. l, or the edge may be flanged as shown in Fig. 2. It is necessary, however, that adjacent that portion of the cap where the cup-shaped portion joins the holding or supporting portion of the cap, a 'weakenedsection be pro vided of which the mechanical opposition offered is less than the lower edge of the cap. This result may be obtained in a variety of ways.

In the form shown by Fig. 1, there is a it is obvious, of course, that the perforations 9 alone will perform the function desired, or they may be combined with an insulator cap through an opening 16, would tend to de' having a thin portion 8 in addition to the apertures. Another form is shown in Fig. 3 in which the cap is provided not with a thin section extending entirely around the cap, but with a plurality of thin sections 10 spaced apart on the inside of the cap, which would accomplish substantially the same result as the forms shown in Figs. 1 and 2 but would have portions between the thin sections designated by the reference numeral 11 in Figs. 3 and 4, which are of substantially the same thickness as the remainder of the wall'of the insulator cap, and even if one or more of the thin sections 10 did blow out, the other portions 11 would serve to hold the insulator in place within the cap.

In Fig. 5, an insulator cap is shown with weakened sections 12 formed by partially severing or slotting the wall of the cap, the cuts 13 in this figure extending entirely through the wall but not joined entirely around the weakened section 12, so that the weakened section 12 is held rigidly in place under normal operating conditions. It is obvious, of course, that the same result would be produced if the cuts did not extend entirely throughthe wall of the cap.

If the weakened section consists of an opening through the wall of the cap, it is advisable, if not absolutely necessary, to fill the opening proper with some material 14: as more clearly shown in Figs. 6 and 7 In all of these forms, it is presumed, of course, that the insulator'is secured to the cap by means of cement 15, which, if left exposed teriorate if moisture enteredthe cap through the opening. It is'gcontemplated that this material might be metal, cement or .any other suitable substance which will blow out before a dangerous pressure is reached within the metal cap.

The interior of the insulator head 5 is commonly formed with a recess 17 in which a metal suspending pin 18 is inserted. The metal pin and the cap '7 are preferably formed with ribs or projections 19 and 20 which serve to'anchor the cement 15 more rigidly to them. The insulator itself may also be provided or formed on its attaching surfaces, with projections 21 which also provlde an anchoring surface for securing the cement 15 more rigidly to the insulator.

It is obvious that if the upper wall of the suspending cap is very thick, an arc would have difliculty in eating its way through this portion of the wall, and the pressure within the cap might reach such a degree that the pin or the porcelain itself might be forced out of the cap. If the wall is thin in the upper portion, the arc will eat through it more readily, causing an opening which will permit the escape of gases. If the upper portion of the cap is thin enough, the pressure set up by an abnormal electrical voltage or by any pressure, due to the relative expansion or contraction of the parts, set up within the cap will cause it to burst open at the thin or weakened portion before there is any danger of bursting the entire cap and separating the cap from the insulator or before blowing the pin or cap loose from the insulator. This is exceedingly important in operating an electrical transmission line, for practically every mechanical failure which would cause the line suspended by the insulater to drop, means an interruption to the electrical service. Since there are many thousand insulator units in a transmissionline, it is evident that an equivalent percentage of mechanical failures would cause an impossible operating condition. On the other hand, many separate insulator units might'be defective electrically, but unless there is an excessive number of defective insulating members in a string or series of insulating units, there would be no trouble or interruption to the normal electrical service, since one or more of the units of such aseries might fail electrically when subjected. to'high or abnormal pressure or discharges, without impairing the electrical operation of the insulator under normal working voltage.

The present invention provides an insulating unit which may be defective electrically but which, when operated in connection with a series of similar insulating units which are not defective, will properly insu-- late the line under normal operating conditions without allowing the mechanical separation of the parts of the defective insulator unit.

I claim: 1

1. In an insulator of the class described, ametal suspension cap having a predetermined weakened portion which will give under pressure before other portions of the cap.

2. In an insulator of the class described, a metal suspension cap,and an insulating member secured therein, the cap being formed with a predetermined portion mechanically weaker than other portions which permits a greater expansion of the insulating member than the other portions of the cap.

3. In an insulator, the combination with a metal suspension cap formed with an attachment cup with a predetermined thin portion, and an insulating member inserted and secured in the cup portion, the thin portion being adapted to relieve pressure due to relative expansion of the cap and member.

4. In an insulator, the combination with a metal suspension cap having a cup-shaped attachment portion with spaced perforations at a distance from the edge of the cup, and an insulating member secured in the cup of the suspension cap, the perforations l l l l l l l distances apart.

1 i being adapted to relieve pressure due to relative expansion of the cap and member. 5. In an insulator of the class-described,

' a metal suspension cap having a cup-shaped attachment portion, formed'with a thin portion at a distance from the edge of the said attachment portion and with perforations at spaced distances apart from the edge of the said, portion, and an insulating member secured within the said attachment portion.

6. A suspension cap for an insulator consisting of a metallic cup-shaped portion having a predetermined thin portion at a distance from the edge of the cup with perforations in the thin portion at spaced 7. In an insulator, the combination with a metal suspension capformed with a suspension cup-havingawall portion of weakened mechanical structure about the top at a distance from the edge of the cap, of an insulating member having a boss insertible within the cap, and cement for securing the insulator within the cap, the said weakened portion yielding under strain due to the relative expansion of the material within the cap.

8. In an insulator, the combination with a metal suspension cap having rigid edge and a comparative tion at a distance from the edge, of an insulating member insertible within the cap, and a cement for securin the insulator within the cap to both the rigid and weaker portions thereof whereby the expansion of they material within the cap will burst a cupwith a y weaker por- U through the weakened section of the cap but aration from the cap even though the insulation is broken through the member between the pin and the cap.

.10. In an insulator, a frangible insulating member, and a suspension cap in which the member is secured having a predetermined thin portion at a distance from the edges of the cap which will burst under pressure before the other portion of the cap.

11. A metallic suspension cap for an inw sulator having a plurality of perforations at a distance from the edge thereof to relieve the pressure due to the relative expansion of any material within the cap.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, on this 9th day of May, A. D. 1916' s ARTHUR O. AUSTIN.

Witnesses:

E. B. SNYDER GEORGE WILLIs. 

